I received a copy of the book recently, and found the rest of it very interesting. Maarten Kossmann and Ramada Elghamis discuss the traditional Arabic orthography of Tuareg, which shows several unexpected features. Two articles discuss the writing of Afrikaans in Arabic script, which – hard as it may seem to believe – predates its writing in Latin script. Nikolai Dobronravine discusses the use of Arabic to write African languages (as well as the Arabic language) in the Americas – the archives of Brazil, for example, contain a surprising number of letters confiscated from slaves. Other articles examine Fulani, Kanembu, Manding, and Swahili, as well as the history of Arabic writing in general and its distribution in Africa.
On a related note, if you're interested in Libyan Berber, it turns out there's a surprisingly large number of people writing even some of the least well-known varieties on Facebook, often in Arabic script; see my recent post on Awjili negation for Awjila, or Awal n ɛdeməs for Ghadames.